A halo implant is typically utilized to implant dopant on a semiconductor device. In-line lithography or DUV (deep ultra violet) photoresist is typically utilized to mask the halo implant process. Typically, the same mask (lightly doped drain) (LDD) is utilized for the halo implant, since the halo implant takes place after the LDD implant. Due to the chemistry of the photoresist, an implant shadowing problem oftentimes occurs utilizing conventional processes (mask & photoresist set), which adversely affects yield and performance of the devices as manufacturing processes move toward smaller geometries.
The first problem is that the photoresist thickness in the area of implant is of a thickness such that an implant delivered at a 45° angle can result in an asymmetric and leaky transistor. A second problem is the thickness of the photoresist related to the trench oxidation region of the device. Accordingly, if a thick photoresist (0.55 μm or greater) is placed over the trench oxidation, due to the soft jelly type nature of the photoresist oftentimes the photoresist will fall and cover areas that are to be implanted. Even if the photoresist stands erect at the smaller process technologies, the halo implant will not reach the targeted areas. In addition, the conventional processes do not typically account for the need for selective doping of the source/drain area.
Accordingly, what is needed is a system and method for overcoming the above-identified problems at smaller process geometrics. The present invention addresses such a need.